98 SMITPISONIAN MISCItLLANCOUS COLLKCTIONS VOL. 35. 



The reference of this shell to Xisusia is based on the evidence of 

 the presence of a prolonged beak and the character of the ribs. The 

 genus is doubtful, but I do not know of any other to which a tenta- 

 tive reference could be made. 



Formation and Localjty. — Upper Cambrian: Thin-bedded lime- 

 stones just below the base of the Ordovician ; Lower Kanab Canyon,, 

 where it enters the Grand Canyon of the Colorado, Northern Ari- 

 zona. 



NISUSIA (JAMESELLA) LOWI, new species 



Plate 9, Figure 14 



In form, outline, convexity, and cardinal area of the ventral valve 

 this species resembles Nisusia festinata (Billings) [1861^, p. 10]. 

 The surface of iV. (Jainesella) lozvi differs from that of iV. festinata 

 in having more and finer radiating ribs, clearly defined, rounded con- 

 centric striae and lines of growth, and the absence of all traces of the 

 surface spines, so characteristic of N. festinata. The latter is also' 

 a larger species. N. (/.) lozvi averages 10 to 12 mm. across the 

 hinge line and rarely over 8 mm. in the length of the ventral valve 

 of the large shells of the species. 



The specific name is in honor of Hon. A. P. Low, Deputy Head 

 and Director of the Geological Survey of Canada. 



A'isusia (Jainesella) lozvi occurs at horizons 186 to 294 feet (56.7 

 to 89.6 m.) above the horizon of Nisusia festinata in the Mount 

 Stephen Section. 



Formation and Locality. — Lower Cambrian: (i) About 5 feet 

 (i.j VI.) belozv the top of the Lozver Cambrian, in thin-bedded lime- 

 stones of Mount IVhyte formation; (2) drift block of limestone sup- 

 posed to have come from the horizon of (i) ; and (3) about 50 feet 

 (15.2 m.) below the top of the Lower Cambrian, in shales of Mount 

 Whyte formation ; all three from north shoulder of Mount Stephen, 

 just above the tunnel, on the Canadian Pacific Railway, 3 miles 

 (4.83 km.) east of Field, British Columbia. (4) About 160 feet 

 (48.8 m.) below the top of the Lower Cambrian, in oolitic lime- 

 stones of Mount Whyte formation, slopes of Mount Bosworth, a 

 little north of the Canadian Pacific Railway track, between Stephen 

 and Hector, British Columbia. 



WIMANELLA, new genus 



This genus is proposed for the smooth, non-plicate species that I 

 have heretofore referred to the genus Billingsella. Vf'^imanella rep- 

 resents the smooth, early stages of development and Billingsella the 



